The overall goals of this research program are to develop chemical sensors for compounds of neurochemical importance, and to use these sensors to explore new aspects of brain chemistry. The primary methods that will be used are electroanalytical techniques. These methods can be directly applied for the determination of the easily oxidized biogenic amines. Furthermore, we have shown that the electrodes can be miniaturized for use as in situ probes of the chemical dynamics of neurotransmitter interactions. The specific aims that will be addressed in this project period are: interactions. The specific aims that will be addressed in this project period are: 1. The design of electrodes and voltammetric techniques which exhibit increased specificity for neurochemical substances. Work in this area is a continuation of that in the previous proposal and is based on the principle that surface treatment of electrodes can by used to prepare sensors suitable for the determination of neurochemicals. Polymeric coatings will be designed to limit access to the electrode surface of undesired species. Various surface modifications, established in the electroanalytical literature, will be adapted for specific neurochemical substances. An enzyme-based amperometric electrode for acetylcholine will be miniaturized for use in the intact brain. 2. Measurement of chemical changes with micrometer spatial resolution. The microvoltammetric electrodes developed in this laboratory are capable of the determination of concentration changes with considerable spatial resolution. We plan to use this attribute in two applications related to neurochemistry. First, we plan to use carbon fiber electrodes as detectors for compounds separated on conventional high performance columns. The goal of this research is to demonstrate the mechanisms which cause chromatographic bands to be broadened. Second, we plan to use these electrodes to probe the secretion of catecholamines from single, isolated adrenal cells. The high degree of spatial resolution should allow direct measurement of release in real time. 3. Measurement of the dynamics of 5-hydroxytryptamine in brain tissue. During the present project period we have developed a sensitive and selective method for the detection of this neurotransmitter with carbon fiber electrodes. This method will be used to probe the extracellular concentration of this substance both in the brain of anesthetized rats and slices prepared from rat brain tissue. In this way the factors which regulate the actions of 5-hydroxytryptamine will be probed.